let's bring in our senior medical correspondent, elizabeth cohen. she's in flower mount, texas, right now, with some details of one very sad, fatal case. elizabeth, what happened? >> reporter: wolf, you know, flu can be insidious. and it can attack even perfectly healthy people. and here's the story of one young man who got very sick, very quickly. this family was getting ready for a joyful christmas when on december 21st, 17-year-old son max started feeling sick, tired, fever. >> never really got like super sick. >> two days later, he was feeling better, played in the snow on vacation in wisconsin, celebrated christmas with his family. but christmas night, max felt sick again. >> he had excessive, like 104.9 fever, and we could not break it. >> reporter: the next morning, his parents took max to the hospital, where he was diagnosed with the flu. >> within 30 minutes, i mean, the doctor was like, something's really wrong here. his kidneys are starting to fail. >> max was rushed by helicopter to a larger hospital. >> one of the last coherent things h